1. Field of the Invention
The present invention relates generally to extracting component signals from a composite signal and, more specifically, to a method and assembly for extracting and identifying component signals from their responsive sources.
2. Description of the Related Art
There are many instances when it is desirable to analyze a signal. This is especially true in the automotive field when determining how much noise is going to be heard by the occupants of a motor vehicle. Depending on the level of noise, it is often a desire to reduce the noise to provide a motor vehicle with quiet operating characteristics.
Eliminating noise can best be accomplished by eliminating the source of the noise. Because noise, especially in motor vehicles, is a composite of many different noises, the source is often difficult to identify. Noise in motor vehicles is generated by its powertrain, the interaction between the road and the tire, and the wind it creates and drives through. These three types of noise have different characteristics and are, often times, random because they depend on so many variables which are also random. For example, the overall noise at a specific speed may have a substantially different characteristic if the powertrain is providing a substantial torque at that speed. Likewise, the overall noise may be affected by the condition of the road on which the motor vehicle is traveling. Therefore, there is a need to isolate the sources of the overall noise under various vehicle operating conditions to best eliminate it.
U.S. Pat. No. 5,419,198 to Pla discloses an electronic signal enhancement and separation assembly for machinery diagnostics. This assembly utilizes a sensor at each noise generator, namely a rotating shaft. In the embodiments contemplated by Pla, all of the noise generators were rotating shafts. The signals generated by the sensors were fed through an adaptive filter which modified itself based on the activity of the noise generator. This adaption allows the filters to more accurately identify the portion of the noise generated by each individual rotating shaft. This assembly only senses rotating objects, i.e., rotating shafts. Therefore, its usefulness is limited when used in an environment such as a motor vehicle. Although useful in detecting noise generated by a driveshaft, noise generated in a motor vehicle by other sources is random and an assembly that is capable of sensing periodic noise having a very small random component is not useful due to the time it takes to adapt to the randomness of the noise. More specifically, by the time the assembly adapts its filter to the noise in the motor vehicle, the motor vehicle will be in another condition generating a different type of noise for which the filter cannot adapt quickly enough. Therefore, there exists a need to adapt a filter quickly to react to the randomness of the signal it is filtering while accurately extracting the component of the noise signal for which it is designed.